This updates the third-party library nanobench with the latest release. It contains mostly minor bugfixes, a new pyperf output format, ability to suppress warnings with environment variable `NANOBENCH_SUPPRESS_WARNINGS`. Full changelog:

v4.0.2
* Changed `doNotOptimizeAway` to what google benchmark is doing. The old code did not work on some machines.
* fix: display correct "total" value
* minor Documentation updates

v4.1.0
* Updated link to new pyperf home
* Adds ability to configure console output time unit
*  Add support for environment variable `NANOBENCH_SUPPRESS_WARNINGS`
* Nanobench is now usable with CMake's FetchContent (see documentation: https://nanobench.ankerl.com/tutorial.html#cmake-integration)

v4.2.0
* Ability to store and later compare results added, through `pyperf`.
* See https://nanobench.ankerl.com/tutorial.html#pyperf-python-pyperf-module-output
* Added lots of build targets to travis, similar to bitcoin's build.
* Some minor API & documentation improvements

v4.3.0
* `ankerl::nanobench::Rng` can now return the state with `std::vector<uint64_t> Rng::state()`, and this can also be used to initialize the Rng.

v4.3.1
* Minor cmake improvements when integrationg as a third-party library: add alias `nanobench::nanobench`, default to C++17

v4.3.2
* Fixed a MSVC 2015 build problem
* updates license to 2021.
* build should now work with very old linux headers
* Also disable UBSAN (bitcoin needed to add a suppression)

v4.3.3
* Do not use locale-dependent `std::to_string`